The invention relates to the technical field of lithium battery cathode material preparation, discloses a preparation method of a high-specific-capacity lithium battery cathode material, and solves the problems that a sulfur-containing composite material cannot meet the requirement of rapid charging and discharging, a large amount of auxiliary conductive agent needs to be added, the sulfur-containing composite material is easily dissolved in electrolyte during discharging and the service life of a battery is influenced, the performance of the sulfur-containing composite material in the lithiumbattery is remarkably improved, the performance of the positive electrode material can be effectively improved, the performance of the prepared positive electrode material is comprehensively improved, and the circularity is enhanced. According to the invention, the conductivity of the sulfur-carbon composite positive electrode material is improved, the specific capacity is high, the effective value reaches 1240-1300mAh/g, the sulfur-carbon composite positive electrode material can also show excellent cycle performance at room temperature, the properties of quick charge and discharge, long discharge time, light weight and the like of a lithium battery are further improved, the requirements of modern electronic equipment industry are met, the use amount of a conductive agent is reduced, andcost is reduced.